xfrm: add xdst pcpu cache

retain last used xfrm_dst in a pcpu cache.
On next request, reuse this dst if the policies are the same.

The cache will not help with strict RR workloads as there is no hit.

The cache packet-path part is reasonably small, the notifier part is
needed so we do not add long hangs when a device is dismantled but some
pcpu xdst still holds a reference, there are also calls to the flush
operation when userspace deletes SAs so modules can be removed
(there is no hit.

We need to run the dst_release on the correct cpu to avoid races with
packet path.  This is done by adding a work_struct for each cpu and then
doing the actual test/release on each affected cpu via schedule_work_on().

Test results using 4 network namespaces and null encryption:

ns1           ns2          -> ns3           -> ns4
netperf -> xfrm/null enc   -> xfrm/null dec -> netserver

what                    TCP_STREAM      UDP_STREAM      UDP_RR
Flow cache:             14644.61        294.35          327231.64
No flow cache:		14349.81	242.64		202301.72
Pcpu cache:		14629.70	292.21		205595.22

UDP tests used 64byte packets, tests ran for one minute each,
value is average over ten iterations.

'Flow cache' is 'net-next', 'No flow cache' is net-next plus this
series but without this patch.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c
index 1f9a079e08b0..5cd7a244e88d 100644
--- a/net/xfrm/xfrm_device.c
+++ b/net/xfrm/xfrm_device.c
@@ -153,6 +153,7 @@ static int xfrm_dev_register(struct net_device *dev)
 
 static int xfrm_dev_unregister(struct net_device *dev)
 {
+	xfrm_policy_cache_flush();
 	return NOTIFY_DONE;
 }
 
@@ -175,6 +176,7 @@ static int xfrm_dev_down(struct net_device *dev)
 	if (dev->features & NETIF_F_HW_ESP)
 		xfrm_dev_state_flush(dev_net(dev), dev, true);
 
+	xfrm_policy_cache_flush();
 	return NOTIFY_DONE;
 }